There are many items that can be purchased before travel to make the journey more enjoyable, less expensive and to limit time spent on mundane tasks.

Pre-order tickets to galleries, museums, shows

In many cases, pre-purchasing tickets provides guaranteed entry and avoidance of a queue.
At some sites, demand is so high that entry by queuing 'on the day' may not result in entry.
It is also often important to check opening hours and fees to be sure that you can visit on a day and time that is suitable.
Many museums and galleries in Europe are closed on Mondays, for instance.

Local tourism sources

Most cities and many larger towns have some sort of tourist information office.
There are also local and regional web sites that can provide online advice of attractions, opening times and entry fees.

Travel SIM or global roaming

While you can use your mobile phone with your provider 'global roaming' arrangement, it is possible to use cheaper alternatives.
Some global roaming fees are such that a return from holidays results in bills of thousands of dollars.
Online websites give comparison costs of global roaming vs using a travel SIM.

If you have a spare mobile handset or your handset is not locked to a provider you can use a Travel SIM which is often cheaper and can be ordered online.
Ensure that you check its function on your phone before leaving Australia however.

Mobile phones and data plans can also be hired online for use in the country of travel.

Luggage, safe bags, screened wallets

Purchasing suitable luggage
Travel bags and purses are available that have wired straps and mesh screened bags to prevent easy cutting by bag snatchers.
Mesh screening may also provide protection against short range wireless reading of credit card and passport details.

Electrical adapters

International electrical voltages and frequency vary from 100-240 Volts / 50-60Hz.
Many modern device chargers are designed to cover this range so that tablets and mobile phones can be charged.
However it is necessary to have the correct mains adapter plug for the countries you are visiting so that your device can be plugged in.
Because of electrical safety, online purchases of adapters may be risky unless known brands are selected.
In this it might be safer to use Australian online businesses to ensure electrical compliance.

Clothing

Travel clothing is available that combines fast drying, non-iron and light weight and makes a great travel item (but perhaps not a high fashion garment!)

Luggage locks, straps, neck pillows…

Luggage accessories are all available for purchase online.
Some suppliers will provide pick up in their retail stores if this is more convenient.

[If you are using luggage locks be aware that security services may cut off the locks if they have any concern about your checked luggage.
Travelling to the USA it may be preferable to use the TSA locks that allow security to open without damage]